The Rules of the Outcast

I'm actually writing, at this moment. Except I'm here posting, which is technically writing but not what I'll be doing as soon as I post this. I have a subterranean race and I made the note "Rules of the Outcast" to remind myself to try and figure out what sorts of customs and rules a society that has been expelled from a larger group would develop.

Unfortunately, it's not something I can just google.

So I'm trying to think stuff up myself. But if you have some ideas, I'd love to hear them.